Electric lighting.



PATENTED JULY 9, 1907.

J. HRDEN. ELECTRIC LIGHTING.

APPLIGATION FILED 1330.10, 1903.

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IINITED STATES PATENT OEEICE.

JOHANNES HRDE'N, OF SCHENECTADY, NEW YORK, AssICNoR To GENERAL ELECTRICCOMPANY, A CORPORATION OF NEW YORK.

ELECTRIC LIGHTING.

.Specification of Letters Patent.

Patented July 9, 1907.

To all whom 'it may concem:

Be it known that I, JOHANNES HRDE'N, a subject of the King of Sweden andNorway, residing at Schenectady, county of Schenectady, and State of NewYork,

have invented certain new and useful Improvements in Electric Lighting,of which the following-is a specification.

The object of my present invention is to improve the operation andincrease the efliciency of arc lamps.

- It has heretofore been found that electrodes containing or composed ofcertain substances other than carbon such as titanium or its compoundsare highly efficient sources of light as they give a luminous arc whichyields an intense white light. Difhculty has heretofore beenexperienced, however, in theuse of electrodes formed i of thesematerials in alternating current lamps employing moderate electromotiveforces and current strengths. Y' This is due I believe to the fact thatthese materials are non-arcing. By non-arcing materials I mean materialswhich cannot maintain a steady alternating current arc with current andvoltage strengths of magnitudes which insure a steady arc where directcurrent is employed. I have found that such electrodes can besuccessfully employed in alternating current lamps if means are providedfor properly introducing into the arc certain substances such as carbon,salts of halogens and of the light earths or the like which willmaintain an alternating current having the same voltage and currentcharacteristics as a direct current arc maintained therefrom.

` It is desirable that the arcing Inaterials introduced shall not havethe effect of appreciably lowering the melting point of the electrodes,as where the melting point of electrodes is lowered far enough to allowthe formation of a pool of melting material at the electrode tip, anunsymmetrical How of current is apt to occur.

I have found an advantageous way of carrying out my invention to consistin employing an electrode composed essentially of a non-.arcingmaterial, such as a titanium compound or the like, in combination with asecond electrode composed principally of a suitable arcing material suchas carbon. The first electrode may have a comparatively small percentageof some arcing material such as carbon mixed with the nonarcingmaterial, and the second electrode may consist of a shell of arcingmaterial such as carbon and acomparatively small core composedprincipally of non-arcing material.

The difficulty which has heretofore been experienced in the operation ofelectrodes containing titanium compounds Or the like in alternatingcurrent arc lamps has been due, I believe, to the fact that during theintervals in which the strength of the alternating current is low thearc path, which is filled with vaporous compounds, cools to a pointwhich greatly decreases its conductivity; this necessitates a highelectromotivc force to bring the current again up to its normal maximum.The carbon or other materials which I add to the arc act, I believe, tomaintain the conductivity of the arc path.

For a better understanding of my invention reference may be had to theaccompanying drawing and detailed description in which I have`disclosedone embodiment of my invention.

The drawing is an elevation, partly in section, showing a pair ofelectrodes between which an arc is main tained by alternating current.

The lower electrode l is formed largely, or wholly, of titanium or itscompounds. Preferably I employ in its formation a mixture containingtitanium carbid and carbon in the proportion of about 90 parts oftitanium carbid to about l0 parts of carbon. The titanium carbid isordinarily formed from rutile, by reducing in an electric furnace. Ifind it desirable to free the carbid thus formed from iron and generallyfrom silicates which it may contain. The presence of iron in theelectrode has a tendency to reduce its melting point. This may result inthe formation of a pool of melted material at the 'tip of the electrodewhich interferes with the proper operation of the alternating currentarc. Silicates usually form slags which are apt to interfere in variousways with the proper operation of the arc. I find, however, that thepresence of a `small quantity of aluminium silicate in the electrode isnot undesirable, as it seems to steady the arc while producing butlittle, if any, injurious consequences. From a plastic mass, containingan intimate mixture of titanium carbid and carbon to which preferably isadded a small amount of a suitable binder such as linseed oil or tar,the electrode is molded, pressed or otherwise formed. The electrode thusformed is heated firstin a muflle furnace in which the temperature isabout 900 C., and then in acarbon tube electric furnace in which thetemperature' is brought up'to about 1800o C. Afterv being graduallycooled the electrode is preferably copper plated and is then ready foruse.

The upper electrode 2 comprises preferably a shell 3 of carbon and thefilling or core 4. The core 4 may be formed of a mixture of titaniumcarbid and carbon above specified, to which a small quantity of asuitable binder, such as Rater glass, mastic or the like, is added. Thecore or filling may be inserted in the shell in any suitable manner. Inpractice I prefer to squirt or press the core into the shell while thematerial composing the core is in a plastic condition. After the core isplaced in the shell the whole electrede is heated to a temperature ofabout 400 or 500 C. in a drying oven. The presence of the lbinder in thecore is desirable as it insures a good mechanical connection between thecore `and the shell'. The core containing titanium carbid is notessential in all cases, but is desirable as it insures the possession bythe arc at all times of the characteristic features of the titanium arc`The electrodes thus formed, When connected to a proper sourceofalternating current, give, with a moderate voltage, a luminous arcyielding a'large amount oi light oi good color. The titanium carbidformed in the manner hereinbeore described may contain other compoundsof titanium such, for instance, as the oxid, or it may contain somemetallic titanium. These substances, however, are not seriously, if atall, objectionable.

The composition oi the electrode I may be varied somewhat from thatgiven above and certain other substances may be added to those therespecified. In particular I have found that electrodes formed from amixture containing about 75 parts of titanium carbid, 10 parts ofcarbon, 3 parts .o ammonium chlorid, 2 parts oi magnesium phosphate andl0 parts of liquid tar, which acts as a binder, give very satis factoryresults. In the process of baking and iring the electrodes the liquidtar is converted into carbon, and as some of the carbon in the mixtureburns away the percentage of carbon in the completed electrode formedfrom this mixture is about l2 per cent. Small amounts oi ammoniumchlorid and magnesium phosphate may be employed in thecore oi theelectrode 2 ii desired.

I am aware that it`has heretofore been proposed to place in one or bothof the carbon electrodes between which an alternating current ismaintained, certain so-called light-producing salts, such as those oflime andmagnesia, in orden that the arc between the electrodes may becolored. In such cases however the salts are merely evaporated into' theare by the heat produced. The arc is essentially a carbon arc colored bythese substances. My present invention is to be clearly distinguishediromsuch cases, as the titanium carbid or the like used by me is aconducting compound which is ionized by the current.' The ionized vaporthus formed serves as the principal gaseous medium through which currentbetween the electrodes passes. p

The electrodes which l have hereinbeiore described may be advantageouslyemployed in the lamp mechanism shown in my application for patent on arclamps, Serial No. 184,876, iiled on the 12th day oi December, 1903,although it is not essential that they be employed in any particularform oi lamp.

What I claim as new and desire to secure by Letters Patent of the UnitedStates, is:

1. In combination for use in an alternating current arc lamp, anelectrode composed principally of some nolnarc ing material which givesa lu'minous or naming are, and

an electrode composed principally of arcing material and containing somesubstance which gives a luminous or flaming arc.

2. In combination for use in an alternating current arc lamp. anelectrode containing a predominating amount of titanic material, and anelectrode composed principally of carbon..

3. In combination for use in an alternating current arc lamp, anelectrode containing a predominating amount of titanium carbid, and anelectrode composed principally of carbon.

4. lIn combination for use in an alternating current arc lamp, anelectrode containing a large proportion of titanic material. and asecond electrode composed principally, of carbon, but containing sometitanic material.

5. In combination for use in an alternating current arc lamp, a pair ofelectrodes'. one of said electrodes being formed of a homogeneousmixture of carbon and titanium vcarbid undthe other of said electrodesconsisting of a core purt` und a shell part. oneof said parts being com'posed principally of carbon und the other of said parts being` composedprincipally of titanium carbid.

6. in combination for Ause in an alternating current arc lump. anelectrode containingn large proportion of titanium carbid and a smallproportion of carbon, and a second electrode containing a largeproportion of carbon and a small proportion of titanium carbid.

7. In combination for use in an alternating current arc lamp, anelectrode composed principally of a chemical compound of titanium, and asecond electrode composed principally of carbon but containing sometitanic material4 S. In combination for use in un alternating currentlamp, an electrode composed principally of carbon, and an electrodecomposed principally of titanium carbid but containing small quantitiesof carbon, ammonium chlorid and magnesium phosphate.

0. An electrode for use in alternating current lamps. consisting of aconducting substance which gives a luminous arc but is non-arcing withalternating current, with the addition of a substance able to maintainan alternating arc in a percentage great enough to make the electrodeoperate with alternating current.

IO. In combination for use in an alternatingl current arc lamp, a pairof electrodes, one of said electrodes being formed of a homogeneousmixture of carbon and titanium carbid, and the other of said electrodescomprising a shell ofcarbon and a core containing titanium carbid.

11. in combination for use in an alternating current arc JOHANNESniiunrm.

Witnesses: v l

BENJAMIN B. HUL Bnu'roN C. ANTHONY.

